The invention is directed to the field of high-power lasers and, more particularly, to a face cooled optic cell for use in laser cavities.
High-power laser systems are used to effect major changes in objects. Example applications of high-power laser systems include materials working, electronics manufacture, medical treatment, nuclear fusion and laser weapons.
In high power laser systems, mirrors and lenses that steer and transmit the laser beam are exposed to extremely high levels of optical power throughput and intensity. The substrate and substrate coatings of these optics are formed of materials carefully selected to minimize the absorption of energy from the laser beam. Despite these measures, most glass substrates and anti-reflective coatings absorb some very small fraction of power from the laser beam, resulting in their heating. This heating is detrimental to critical optics in the laser resonator, because the prescription of these optics change with temperature due to thermal expansion. The resultant dimensional changes caused by thermal expansion can ultimately produce beam distortion, unwanted beam steering and damage to components.
The physical properties of optical materials make it extremely difficult to remove heat from the optics during operation. Particularly, transmissive optical materials have very low thermal conductivities. Consequently, large thermal gradients occur in these materials during laser operation. Large thermal gradients and high surface temperatures in optics can cause localized convection currents in the surrounding air, resulting in instabilities in the beam. Hence, at some design value of optical throughput and intensity, it is necessary to provide cooling to the optics so they maintain their prescriptions and design temperatures during laser operation.
The cooling of optics can be either active or passive. Active cooling systems have a number of important disadvantages, including problems related to vibration and temperature control. In order to make the temperature control system function properly, special materials, coolants and instrumentation are required. These requirements increase the complexity and cost of the temperature control system. Passive cooling systems for optical elements provide the advantage of being less complex than active systems. Known passive cooling systems, however, are less than fully satisfactory.
Thus, there is a need for an improved cooling assembly for optic elements in high-power laser systems that (i) is passive and has a simplified construction; (ii) minimizes heating of the optic element due to absorption of laser light during laser operation; (iii) reduces localized convective currents near the surface of the optic element; and (iv) reduces temperature gradients in the optic element substrate.